A system for determining the weight of an occupant on a vehicle seat is known. The system outputs a signal indicative of the weight of the occupant to a controller. The controller controls actuation of a vehicle safety device, such as an air bag or pretensioner. The controller, upon the occurrence of a crash condition, considers the weight of the occupant when determining whether the vehicle safety device is should be actuated. The vehicle safety device is actuated when the weight on the seat is determined to be greater than a threshold level.
When a child safety seat is located on the seat, it may be desirable to prevent actuation of the vehicle safety device. Typically, seat belt webbing associated with the seat holds a properly installed child safety seat is firmly on the seat. The tension of the seat belt webbing holding the child safety seat on the seat may result in the weight sensed by the vehicle occupant weight sensor being above the threshold level. When the tension in the seat belt webbing is known, the controller of the system may determine a “true” weight on the seat by subtracting the load on the seat caused by the tension in the seat belt webbing from the weight sensor measurement.